Methods employed in conventional pixel interpolation devices used in the above situations to calculate interpolation data for missing pixels include a method in which the mean of the values of the pixels adjacent to a missing pixel is used as the interpolation data, a method in which a regression line is found for the pixels adjacent to a missing pixel by use of the least squares method and the interpolation data are calculated from the regression line, and a method in which a quartic curve is found from the four pixels adjacent to a missing pixel and the interpolation data are calculated from its quartic equation (see, for example, Patent Document 1), but it is difficult for these devices to interpolate periodic data.
As an improvement, the interpolation of periodic data by determining interpolation data for a missing pixel such that the mean value of a plurality of pixels including the missing pixel becomes equal to the mean value of a plurality of pixels excluding the missing pixel has been proposed (see, for example, Patent Document 2). A further proposal is adaptive switching of the interpolation method by providing a plurality of interpolation circuits with differing characteristics, a marking circuit, a management circuit, and an output circuit, wherein each of the plurality of interpolation circuits generates interpolation data for the missing pixel and pixels in the vicinity of the mixing pixel, the marking circuit generates marking data based on the interpolation data respectively output by the plurality of interpolation circuits for the pixels in the vicinity of the mixing pixel and the corresponding original data of the pixels in the vicinity of the mixing pixel, the management circuit generates a selection signal for selecting one from among the interpolation data for the missing pixel output by the plurality of interpolation circuits, based on the marking data output by the marking circuit, and the output circuit outputs, as the missing pixel data, the selected one from among the interpolation data for the missing pixel output by the plurality of interpolation circuits, based on the selection signal output from the management circuit (see, for example, Patent Document 3).    Patent Document 1: Japanese Patent Application Publication No. 2003-101724 (pp. 5-6, FIGS. 3-5)    Patent Document 2: Japanese Patent Application Publication No. 2005-141611 (pp. 3-7, FIG. 1)    Patent Document 3: Japanese Patent Application Publication No. 2005-117291 (pp. 7-8, FIG. 1)